They're appealing to Congress to pass comprehensive immigration reform to avert what they describe as a crisis.

Our immigration system is broken; it can only be fixed at the federal level. We urge Congress to immediately address this issue that is so important for jobs and for our business community.

- Larry Wooten, President of the North Carolina Farm Bureau

The leaders took part Monday in what was billed as the first immigration summit in the Southeast, where agricultural businesses are prevalent and where an increasing number of immigrants -- many undocumented -- have settled in the last decade.

The summit, titled "Forging a New Consensus on Immigrants and America," drew nearly 200 business owners, farmers, clergy, political leaders and police from such states as Alabama, Florida, North Carolina, South Carolina, Tennessee as well as Georgia, the site of the gathering.

“Agriculture is a very labor-intensive industry," said Larry Wooten, president of the North Carolina Farm Bureau. "Farmers across the nation want — and need — an adequate, legal work force. Our immigration system is broken; it can only be fixed at the federal level. We urge Congress to immediately address this issue that is so important for jobs and for our business community.”

Wooten told the audience that states must not have their own immigration laws because it is a complex matter as necessary for the federal government to take control over as are things such as "managing our military or our money supply."

He said agriculture is a $70 billion industry, with more than one million workers, of whom nearly 75 percent are undocumented.

He balked at the assertion by proponents of strict immigration enforcement that businesses that heavily employ undocumented workers are simply choosing to exploit cheap labor.

Many proponents of strict immigration laws say that Americans will do jobs they are accused of refusing to do if employers pay better wages and make more of an effort to make those jobs appealing. Such proponents are firmly opposed to immigration measures that would give undocumented immigrants a pathway to legalization; they condemn that as "amnesty."

Wooten, as well as others in the farming business who attended the summit, argued that there are jobs Americans do not want to do, and that agricultural jobs are chief among them.

He said that agricultural employers who advertise jobs -- as is required for those who are part of the federal guest worker program -- for nearly two months get little to no response.

"We have no choice," Wooten said. "We must use immigrants."

Tim Rabon, human resources manager for a family farming business in South Carolina that, like others in the industry, heavily relies on immigrant workers, said in an interview with Fox News Latino that his company advertised work in Mississippi for six weeks and got 15 responses.

"Some people just didn't qualify, even though harvesting is not 'highly skilled' labor. It is very specialized and you need to be really skilled," Rabon said. "It's very hard work. Those who did qualify didn't last long -- they just quit. The person who lasted the longest stayed on the job five days before quitting. Why did they quit? They said the work is just too hard."

He said tougher immigration laws -- or the prospect of a state adopting a tough immigration law -- have scared away many immigrants, including some workers and prospective employees.

As recently as three years ago, he said, his farm company -- which harvests greens, such as collard and kale -- had no trouble attracting about 20 people a week looking for work.

Now, they barely get one or two people, he said, because so many immigrants have fled the state or are afraid to seek employment.

Rabon says his company has been in farming 85 years, and makes sure to check employment eligibility documents when considering hiring someone. They have about 120 employees, he said.

"If someone presents documents that appear valid, we have to accept them," he said.

Summit organizers hope to hold such gatherings around the country to build up momentum for Congress to pass comprehensive immigration reform, which would include tighter, more focused enforcement as well as a pathway to legalization for undocumented immigrants who meet a strict set of criteria.

The summit was held as the U.S. Supreme Court prepares to issue a decision on Arizona's law, SB 1070, which is aimed at cracking down on illegal immigration by criminalizing it. The U.S. Department of Justice, which brought a lawsuit challenging the law, argues that it usurps federal authority on immigration. The Supreme Court ruling, expected by the end of June, is expected to influence whether other states attempt to pass their own immigration laws.

More than 30 states considered new laws targeting illegal immigration last year, according to the National Conference of State Legislatures. Most of them were modeled after Arizona's Senate Bill 1070.

Census figures show that Hispanics -- who now are the nation's largest minority group, at 48 million -- contributed more to population gains than blacks in 13 of the 16 Southern states over the last decade, compared with seven states for Hispanics from 1990-2000.

Tensions -- over immigration, measures proposing English as the official language -- have arisen along with the growth of Latino presence in these Southern states.

"The Department of Justice is challenging Arizona’s law, arguing that it is intruding on the federal government’s exclusive authority to make and enforce immigration laws," said former U.S. Attorney General Alberto Gonzales, who served under President George W. Bush and was the summit's keynote speaker. "But with authority comes also responsibility, and our national leaders have failed us. It's time for our federal officials to step up, show leadership and pass comprehensive immigration reform.”

There are an estimated 12 million undocumented immigrants in the United States. Roughly half are people who enter legally, but overstay their visas.